A new species of baenid turtle from the Early Cretaceous Lakota Formation of South Dakota

• Main Authors: W. G. Joyce, Y. Rollot, R. L. Cifelli
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-02-01
• Series: Fossil Record
• Online Access: https://www.foss-rec.net/23/1/2020/fr-23-1-2020.pdf
• ISSN: 2193-0066; 2193-0074

<p>Baenidae is a clade of paracryptodiran turtles known from the late Early Cretaceous to Eocene of North America. The proposed sister-group relationship of Baenidae to Pleurosternidae, a group of turtles known from sediments dated as early as the Late Jurassic, suggests a ghost lineage that crosses the early Early Cretaceous. We here document a new species of paracryptodiran turtle, <i>Lakotemys australodakotensis</i> gen. and sp. nov., from the Early Cretaceous (Berriasian to Valanginian) Lakota Formation of South Dakota based on a poorly preserved skull and two partial shells. <i>Lakotemys australodakotensis</i> is most readily distinguished from all other named Late Jurassic to Early Cretaceous paracryptodires by having a broad, baenid-like skull with expanded triturating surfaces and a finely textured shell with a large suprapygal I that laterally contacts peripheral X and XI and an irregularly shaped vertebral V that does not lap onto neural VIII and that forms two anterolateral processes that partially separate the vertebral IV from contacting pleural IV. A phylogenetic analysis suggests that <i>Lakotemys australodakotensis</i> is a baenid, thereby partially closing the previously noted gap in the fossil record.</p>